[gdal-dev] Remapping nodata

[Blumentrath, Stefan]

Hi,

This is also an issue for PostGIS: https://trac.osgeo.org/postgis/ticket/828

You could try a VRT:
gdal_translate -of VRT -a_nodata 99999 your_raster.tif your_raster.vrt
which is pretty efficient (fast and does not duplicate your data), esp. if you have a bigger raster and do not need to reproject...

Cheers
Stefan

-----Original Message-----
From: gdal-dev [mailto:gdal-dev-bounces at lists.osgeo.org] On Behalf Of Even Rouault
Sent: 7. januar 2016 10:42
To: gdal-dev at lists.osgeo.org
Subject: Re: [gdal-dev] Remapping nodata

Le jeudi 07 janvier 2016 08:54:17, Julien Michel a écrit :
> Well, maybe this is a little off topic for the gdal mailing list, but 
> I recently had to deal with the same case, and wrote a small 
> application in Orfeo ToolBox (>5.2) to do exactly that: map NaN to a 
> real no data value [1]. So if you need this really quick, and can 
> afford bringin another (quite big) tool in your workflow, here is a workaround.
> 
> In the long term, this would be a nice addition to gdal_translate 
> capabilities.

This can actually be done with gdalwarp.

$ cat in.asc
ncols        2
nrows        2
xllcorner    440720
yllcorner    3751200
cellsize     60
NODATA_value nan
 nan 123.0
 115 132

$ gdalwarp in.asc out.tif  -dstnodata 0 -overwrite

(if using trunk please update to the latest revision as I just discovered and fixed a bug for this very particular case (float32 and 0 as target nodata). 2.0 works fine)

$ gdal_translate out.tif /vsistdout/ -of aaigrid
ncols        2
nrows        2
xllcorner    440720.000000000000
yllcorner    3751200.000000000000
cellsize     60.000000000000
NODATA_value  0
 0.0 123
 115 132

(you likely need a recent enough GDAL version so that NaN is correctly dealt
with)


> 
> Regards,
> 
> Julien
> 
> [1]
> https://www.orfeo-toolbox.org/CookBook/CookBooksu61.html#x85-1900004.1.7
> 
> Le 06/01/2016 23:59, Brad Hards a écrit :
> > I'm working on the geopackage elevation extension experiment, and trying
> > to produce some GeoTIFF tiles that get inserted into sqlite.
> > 
> > I need to remap the existing nodata (nan) to some other value that I can
> > insert into a sqlite table as a number (say zero).
> > 
> > I had a long explanation of what I'm doing here, but it is actually
> > explained in the docs: "Note that, if the input dataset has a nodata
> > value, this does not cause pixel values that are equal to that nodata
> > value to be changed to the value specified with this option. "
> > 
> > Is there an easy way to do that conversion?
> > 
> > Brad
> > _______________________________________________
> > gdal-dev mailing list
> > gdal-dev at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/gdal-dev

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